Process of preserving wood.



UNITED STATES ToMAso GIUSSANI,

PATENT OFFICE.

or MILAN, ITALY.

PROCESS OF PRESERVING WOOD.

SPECIFICATION forming part of Letters Patent No. 707,224, dated August19, 1902.

Application filed June 26, 1901. Serial No. 66,15 l. (No specimens.)

To (0% whom it may concern:

Be it known that I, TOMASO GIUSSANI, merchant, a subject of the King ofItaly, residing at 10 Via Palestro, Milan, in the Kingdom of Italy, haveinvented an Improved Process for the Preservation of Wood, of which thefollowing is a specification.

If a liquid which has a point of ebullition above 100--for example,tar-oil, linseed-oil, a solution of metallic salts, or the likeis heatedin an open vessel and maintained at a temperature midwaybetween the saidpoint and 100, no movement of ebullition takes place; but if a piece ofwood is plunged into the liquid a movement takes place upon its surfacesi milar to that of ebullition, but which is, in fact, only the effectof the vapor produced by the wood, owing to the water which it containsand which escapes through the surrounding liquid. If the temperature ismaintained constantly above 100 until all movement has ceased, all thewater which the wood contained will have been expelled from it with theexception of a small quantity,which remains in the form of vapor in thepores of the wood, occupying. them completely after having expelled eventhe air contained therein. If after this point has been reached theliquid is allowed to cool, this small quantity of vaporin condensingforms a vacuu'm,wh ic h necessarily becomes filled by the surroundingliquid, which is forced in by the external at:

mospheric pressure. The-wood is therefore completelyinjected,whatevermay be its form or dimensions or the closeness of its grain. A similarphenomenon takes place even when the wood is not allowed to remain inthe same liquid to complete its cooling, but is removed rapidly andplunged into cold liquid of the same or of a different nature. Thisadvantage is especially important, owing to the fact that it permits ofimpregnatin g the wood with a liquid of any desired density or weighteven if its point of ebullition is less than 100. The transfer of thewood from one vessel to another, although effected rapidly, may beperformed with relative ease, because I- have found that the periodelapsing may vary without prejudicial effect upon the absorption fromten to twenty minutes for large pieces of wood'for example,railway-sleepers, telegraph-poles, or the like. The quantity of liquidabsorbed by the wood may be varied as desired by means of this process,because it may be perfectly regulated by the time allowedv for the coldbath, from which it may be removed as soon as the liquid has beenlowered to a predetermined level. A sufficient degree ofevaporationmaybe obtained by means of the hot bath at a temperature of from 130 to150, lasting from ninety to one hundred and fifty minutes, according tothe nature of the wood.

I will now describe two different methods of carrying my invention intopractice.

First. Using a very dense mixture for the hot bath-for example,anthracene and pitch at a density of from 18 to 26Ba um fit1 eevaporation of the wood is effected as above explained. WVhen the woodis removed from the bath, it carries with it upon its entire surface alayer of some millimeters in thickness,

amounting in the case of a railway-sleeper Second. If two'liquids' ofabsolutely differ j ent nature, density, and weight are placed in thevessel containing the cold bathfor example, a solution of chlorid ofzinc or other salts ata density of 2 to 4 Baum and tar-oil (creosote) ata density of 10 to 14 Baumthe two liquids remain quite separate inaccordance with a well-known phenomenonthat is to say, the lightersolution remains above, while the creosote remains at the bottom, whileeven if they are vigorously stirred the two liquids do not change theirrelative positions. The wood upon being removed from the hot bath istransferred to the cold I It is allowed to remain in this bath until theindicator shows that the level of the liquid has become lowered by theamount previously determined upon. The wood is then raised by mechanismprovided for that purpose until it enters I the solution of salts, whichthen surround it and in which it may remain until its completecondensation and absorption, unless it is desired to limit this to apredetermined amount. The treatment is then finished. The passage of thewood through the three different baths produces a very interestingphenomenon, the result of which is absolutely certain. The tar-oilduring its absorption by the wood carries with it the pitch so much themore readily that it is perfectly soluble in the oil. When the wood istransferred to the solution of salts, these latter enter it, carried inin their turn by the internal condensationgvhich has not ceased, andtraverse the tar-oil which entered previously, becoming intimately mixedtherewith as if it had passed through an ideal filter. The two liquidscannot afterward be separated. The pitch removed from the hot bath is.carried beneath the surface, where it forms an impermeable stratum, asabove explained. The great difficulty of obtaining a perfect mixture oftwo liquids not capable of combination one with the other, and Whichhowever perfectly emulsioned beforehand would berower;

posited upon the surface of the wood and then in immersing the wood in asecond cold bath whereby the surface layer remaining from the first bathis made to penetrate the surface of the wood and thereby form a denseprotecting-layer, substantially as described.

2. The process for preserving wood, consisting in first immersing thewood in a mixture of anthracene and pitch heated to a temperature over100 centigrade, whereby the water contained in the pores of the wood isvaporized, and then in immersing the wood in a second bath consisting oftwo liquids of different densities and incapable of being mixedmechanically whereby the latter liquids penetrate the wood and becomemixed with the material of the first bath, within the pores of the woodand form a dense protecting-layer, substantially as described.

3. The process for preserving wood, consisting in first immersing theWood in a mixture of anthracene and pitch heated to a temperature over100 centigrade whereby the water contained in the pores of the wood isvaporized, and then immersing the Wood in a second bath consisting oflayers of a solution of chlorid of zinc and creosote whereby the latterliquids penetrate the wood and become mixed with the material of thefirst bath within the pores of the wood and form a denseprotecting-layer, substantially as described.

In testimony whereof I have hereunto set my hand, in presence of twosubscribing witnesses, this 13th day of June, 1901.

TOMASO GIUSSANI.

Vitnesses:

l\IICIIELEDE DRAGO, JAs. A. SMITH.

